A MOLECULAR MODELING STUDY OF THE CATALYTIC MECHANISM OF HALOALKANE DEHALOGENASE .1. QUANTUM-CHEMICAL STUDY OF THE FIRST REACTION STEP

The haloalkane dehalogenase of soil bacteria Xanthobacter autotrophicu s is an enzyme, which catalyzes the environmentally important detoxifi cation process, namely-the hydrolytic cleavage of the carbon-halogen b ond. A molecular modeling study has been conducted with the structures of the wild-type enzyme and its mutants in order to investigate the m echanisms of the dehalogenation reaction at molecular level. Semiempir ical quantum chemical calculations have been applied to elucidate the importance of the active site residues for kinetic and thermodynamic c haracteristics in the first step of dehalogenation reaction. The resul ts obtained from these calculations have been compared with previously published experimental results. The strength of the application of mo lecular modeling method for the study of the evolutionary aspects of b iodegradation of organic pollutants is discussed.